Could not find numbers on cartridge cover.

Thanks for reaching out to us! The balance support you have reminds me of the 15-205 3/8" Egress Coil Triple Support. This is used with the 3/8" wide Series 165 Coil Balance. If you are looking to replace the compatible coil balance shoe, I'll need to see a clear photo of it, removed from the window.

You'll need to look for stamps/markings on the metal coil to determine the spring strength needed for the assemblies. Take a look at the video tutorial below for a detailed explanation on how to select he correct coils.